Bug#981186: linux: Enable CMN-600 interconnect on arm64
Hi Vincent, Wookey,
On Wed, Mar 17, 2021 at 10:02:25PM +0100, Vincent Blut wrote:
> Le 2021-03-17 19:24, Wookey a écrit :
> > On 2021-03-17 19:43 +0100, Vincent Blut wrote:
> > > Le 2021-03-17 15:49, Wookey a écrit :
> > > > On 2021-03-17 14:52 +0100, Vincent Blut wrote:
> > > > > Le 2021-01-27 12:57, Wookey a écrit :
> > > > > > Version: Please enable ARM CMN-600 power management on arm64
> > > > > >
> > > > > > This requires CONFIG_ARM_CMN=y
> > > > >
> > > > > Does it really have to be built-in instead of being provided as a module? Last I
> > > > > checked, Fedora and Ubuntu provide it as a module.
> > > >
> > > > No it should really be a module. Perf is driven from userspace so you
> > > > never need to use it before modules can be loaded.
> > >
> > > Agreed.
> >
> > > > I see that
> > > > CONFIG_THUNDERX2_PMU=y
> > > > CONFIG_ARM_SMMU_V3_PMU=y
> > > > are also set as builtins. That's probably wrong too.
> > >
> > > It seems your arm64 kernel config deviates from the one we provide in Debian.
> > > CONFIG_THUNDERX2_PMU is compiled as a module while CONFIG_ARM_SMMU_V3_PMU is
> > > not set, at least in linux 5.10.19-1.
> >
> > Hmm. I was looking at the (built, with CONFIG_ARM_CMN=y) sources for
> > 5.10.9-1 and the (unbuilt) sources for 5.10.19-1. So yes, slightly
> > different and the built version is not up to date any more.
> >
> > If we already have CONFIG_THUNDERX2_PMU=m already then that's great
> > (Ah yes - that's the upstream default). Adding
> > CONFIG_ARM_SMMU_V3_PMU=m would be good too. Adding it as a module
> > should be pretty harmless then at least it's available? I'll set off a
> > build now to check it works.
>
> Enabling ARM_SMMU_V3_PMU as a module should be harmless, indeed.
>
> > > > […]
> > >
> > > > I also checked the state of the other perf configs with the arm kernel team
> > > > and got feedback that we have all the ones that should sensibly be set set once
> > > > CONFIG_ARM_CMN=m
> > > > and
> > > > CONFIG_THUNDERX2_PMU=m
> > > > is added
> > >
> > > This means updating the arm64 kernel config to only include ARM_CMN as a module.
> > > To me it is acceptable for Bullseye as this seems uncontroversial, but note that
> > > I can't speak for the kernel team.
> >
> > Will you ask them, or should I?
>
> I can send merge requests to enable ARM_CMN and ARM_SMMU_V3_PMU if you wish.
>
> > It seems like prodding someone would be good as this was filed back on 27th
> > jan and there have been uploads since, so I guess no-one has noticed till now.
>
> I have been contributing for some time to help the kernel team, but I must admit
> I didn't notice this one (and probably many others).
So just to confirm, were you be able to test with those two changes?
Regards,
Salvatore
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